Heat-resistant metal sheet



Patented June 17, 1930 ITED STATES PATENT OFFICE EARL B. 'WEHR AND CARL C. MA HIJIE, OF MIDDIiETOWN, OHIO, ASSIGNORS TO THE AMERICAN ROLLING MILL COMPANY, OF MIDDLETOWN, OHIO, A CORPORATION OF OHIO No Drawing.

Our invention relates to oven lining sheets' and plates, and sheet iron stove and furnace bodies, which are called upon to withstand the heat that will be developed in ovens used for cooking purposes, domestic heating and the like.

It has been a problem of considerable scope toprovide an inexpensive steel or iron sheet, not expensivelyalloyed, but having a suitable coating thereon which will resist the action within a stove or hot air furnace.

In recent years, the trade has gone to a con siderable extent to vitreous enameled Ware for oven lining purposes, but there are a few products on the market having metal coatings on steel plates, which will withstand the temperature of the oven for a considerable period.

, The difiiculty with the plates last noted,

in which we are most directly interested, lies in the fact that the effect of applying heat to the coatings on the oven plates is to render them quite dark, and also somewhat rough in surface texture. This is a defect both from the point of view of the ultimate life of the I plate,

and also from the appearance point of view within the stove. The darkened and roughened linings are not so easilycleaned, they look grimy, and also fail to reflect heat from the combustion units as efliciently as an oven plate should do. In the same manner, sheet iron stove parts, pipes and the like, will darken and deteriorate.

In a co-pending application, we describe generally and claim a steel or iron sheet or a plane surfaced body of steel or iron coated with zinc aluminum alloy, and we have discovered that such a product has very high value as an oven lining sheet or stove or furnace plate, so much so that even if the coating were to be found in the prior art, (con: trary to the results of our research and our belief in the.premises,) still its application for oven linin stoves and furnace purposes has never ma e itself apparent industrially in this country. Thus we believe it to be our invention to provide as a heat resistant sheet or plate, a piece of metal coated with an alloy of zinc high in aluminum.

The plates are formed of a base sheetof- Application filed September 13, 1926. Serial No. 135,276.

iron or steel,'which has been metal coated by applying thereto a flux, and then a'coating of commercially pure zinc, to which has been added sufiicient aluminum to prevent the formation of spangle, butv in which coating the zinc predominates.

We have found that, taking into consideration manufacturing costs and processes, and cost of materials, that a. coating containing commercially pure zinc with aluminum in proportions around 8% will provide a lining plate for ovens which possesses all of the desired qualities to which we have directed our invention. It is also most satisfactory for other heat purposes.

The ranges in which the aluminum addition greatly improves the product lie within three per cent and around twenty per cent, above which we do not understand that it will be practical to go. The aluminum cannot be too high, as it forms a brittle product within certain ranges where aluminum predominates.

A sheet coated with commercially pure zinc together with say 8% of aluminum, will possess a coating as fully flexible or bendable as the metal itself. A temperature up to around 700- degrees Fahrenheit, for example, will not result in a discoloration or any apparent change in the coating. The coating will be brightand without spangle, although when not polished, it will show hair lines of demarkation between fairly large sized spots approaching the size of a spangle.

A temperature at around the melting point of the alloy will not result in a rupture, but will change the structure of the coating, preserving much ofthe color, but due to recrystallization under the conditions in question, building up a rough, spangle condition. The material of our invention may be used with some advantage, but not so satisfactorily in a number of ways, when made with a spelter consisting mainly of zinc, with the impurities found in .commercial spelters, with the addition of over two per cent of aluminum. Spangle will be present, and there may be aslight change of color after'prolonged heating, but the coating withstands bending most excellently in formation of the plates,

V and does not deteriorate or become drab and dark after prolonged exposure to oven temperatures.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is 2- I Anoven lining plate or sheet, having a steel or iron base coated with an alloy of com- 'mercially pure zinc with aluminum as the main alloying agent, said aluminum being present in proportions to the zincby wei ht of two per cent or more, but less in proportlon v by weight than the zinc.

EARL R. WEHR. CARL C. MAHLIE. 

